<!DOCTYPE html>
<html lang="en" style="height: 100%">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body style=" height: 100%;">

<div style="width: 100%;height: 100%; display: flex;justify-content: center; align-items: center; text-align: center">

    <table>
        <form action="/test" method="post">
        <tr>
            <td colspan="3">
                <span>Gguess Number</span>
            </td>
        </tr>
        <tr>
            <td colspan="3">
                <input type="text" id="v1" name="v1" value="1" readonly/>
            </td>
        </tr>
        <tr>
            <td>
                <input type="button" value="1" onclick=" document.getElementById('v1').value = 1 "/>
            </td>
            <td>
                <input type="button" value="2" onclick=" document.getElementById('v1').value = 2 "/>
            </td>
            <td>
                <input type="button" value="3" onclick=" document.getElementById('v1').value = 3 "/>
            </td>
        </tr>
            <tr>
                <td>
                    <input type="button" value="4" onclick=" document.getElementById('v1').value = 4 "/>
                </td>
                <td>
                    <input type="button" value="5" onclick=" document.getElementById('v1').value = 5 "/>
                </td>
                <td>
                    <input type="button" value="6" onclick=" document.getElementById('v1').value = 6 "/>
                </td>
            </tr>
            <tr>
                <td>
                    <input type="button" value="7" onclick=" document.getElementById('v1').value = 7 "/>
                </td>
                <td>
                    <input type="button" value="8" onclick=" document.getElementById('v1').value = 8 "/>
                </td>
                <td>
                    <input type="button" value="9" onclick=" document.getElementById('v1').value = 9 "/>
                </td>
            </tr>
			<tr>
			    <td>
			    </td>
			    <td>
			        <input type="button" value="0" onclick=" document.getElementById('v1').value = 0 "/>
			    </td>
			    <td>
			    </td>
			</tr>
        <tr>
            <td colspan="3"><input type="submit" value="submit"/></td>
        </tr>
        </form>
    </table>


</div>
</body>
</html>

<style>
input {
    width: 100px;
    text-align: center;
}
</style>